Hemoglobin A1C as a prognostic factor and the pre-diabetic paradox in patients admitted to a tertiary care medical center intensive cardiac care unit

Abstract

Abstract Background Hemoglobin A1C (HbA1c) is a form of glycated hemoglobin used to estimate glycemic control in diabetic patients. Data regarding the prognostic significance of HbA1c levels in contemporary intensive cardiac care unit (ICCU) patients is limited. Methods All patients admitted to the ICCU at a tertiary care medical center between January 1, 2020, and June 30, 2021, with documented admission HbA1c levels were included in the study. Patients were divided into 3 groups according to their HbA1c levels: < 5.7 g% [no diabetes mellitus (DM)], 5.7–6.4 g% (pre-DM), ≥ 6.5 g% (DM). Results A total of 1412 patients were included. Of them, 974 (69%) were male with a mean age of 67(± 15.7) years old. HbA1c level < 5.7 g% was found in 550 (39%) patients, 5.7–6.4 g% in 458 (32.4%) patients and ≥ 6.5 g% in 404 (28.6%) patients. Among patients who did not know they had DM, 81 (9.3%) patients had high HbA1c levels (≥ 6.5 g%) on admission. The crude mortality rate at follow-up (up to 1.5 years) was almost twice as high among patients with pre-DM and DM than in patients with no DM (10.6% vs. 5.4%, respectively, p = 0.01). Interestingly, although not statistically significant, the trend was that pre-DM patients had the strongest association with mortality rate [HR 1.83, (95% CI 0.936–3.588); p = 0.077]. Conclusions Although an HbA1c level of ≥ 5.7 g% (pre-DM & DM) is associated with a worse prognosis in patients admitted to ICCU, pre-DM patients, paradoxically, have the highest risk for short and long-term mortality rates.